Abstract : In WDM backbone networks, the traﬃc pattern evolves constantly due to the nature of the demand itself or because of equipment failures leading to reroute aﬀected connections. In this context, requests are routed greedily using available resources without changing the routing of pre-established connections. However, such a policy leads to a poor usage of resources and so higher blocking probability: new connection requests might be rejected while network resources are suﬃcient to serve all the traﬃc. Therefore, it is important to regularly reconﬁgure the network by rerouting established connections in order to optimize the usage of network resources. In this paper, we consider the network reconﬁguration problem that consists in switching existing connections one after the other from the current routing to a new pre-computed routing. Due to cyclic dependencies between connections, some requests may have to be temporarily interrupted during this process. Clearly, the number of requests simultaneously interrupted has to be minimized. Furthermore, it might be impossible for the network operator to interrupt some connections because of the contract signed with the corresponding clients. In this setting, the network reconﬁguration problem consists in going from a routing to another one given that some priority connections cannot be interrupted. The network reconﬁguration problem without priority connections has previously been modeled as a cops-and-robber game in [5, 6]. Here, we ﬁrst extend this model to handle priority connections. Then we identify cases where no solution exists. Using a simple transformation, we prove that the reconﬁguration problem with priority connections can be reduced to the problem without this constraint. Finally, we propose a new heuristic algorithm that improves upon previous proposals.